沁水盆地南部高阶煤储层渗透率与孔裂隙发育的耦合分析

    Coupling Analysis on Permeability and Pore Fracture Development in High Rank Coal Reservoirs of Southern Qinshui Basin

    • 摘要: 为分析高阶煤储层渗透率与孔裂隙发育的耦合关系,以沁水盆地南部3#煤储层为研究对象,采用分形理论研究了孔隙的分形特征,利用几何分形模型计算了不同孔径孔隙对煤岩渗透率的贡献比例,线性拟合了渗透率与孔隙分形维数、体积百分比和镜质组最大反射率Ro,max等因素的相关关系。研究结果表明:孔裂体积以微、小孔为主,比表面积比以微孔最高;孔隙类型以半封闭孔为主;煤样孔隙度平均为4.652%,渗透率平均为8.68×10-5 μm2,大孔和裂隙对渗透率的贡献平均为99.809%,沁水盆地南部3#煤储层渗透率主要来自于大孔与裂隙的贡献;渗透率、孔隙度与Ro,max之间具有较弱的相关性,随着变质程度的增加先上升再下降;渗透率与中孔、大孔和裂隙的分形维数呈正相关关系,与微小孔分形维数呈负相关关系。

       

      Abstract: To analyze the coupling relationship between permeability of high rank coal reservoir and pore and fracture development, taking No.3 coal reservoir in southern Qinshui Basin as the research object, and pore structure was studied by fractal theory. Fractal characteristics, using geometric fractal model to calculate the contribution ratio of different pore size to coal and rock permeability, linearly fitting the correlation between permeability and pore fractal dimension, volume percentage, Ro,max and other factors. The results show that the pore-fracture volume is mainly micro-pore, and the specific surface area ratio is the highest; the pore type is mainly semi-closed pore; the average porosity of coal sample is 4.652%, and the average permeability is 8.68×10-5 μm2. The contribution of macro-pore and fracture to permeability is 99.809%, and the permeability of 3# coal reservoir in southern Qinshui Basin is mainly comes from the contribution of macropores and fractures. There is a weak correlation between permeability, porosity and Ro,max, which increases first and then decreases with the increase of metamorphic degree. Permeability is positively correlated with fractal dimension of mesopore, macropore and fracture, and negatively correlated with fractal dimension of micropore.

       

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